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Tryptophan-derived catabolites are responsible for inhibition of T and natural killer cell proliferation induced by indoleamine 2,3-dioxygenase.

Frumento G, Rotondo R, Tonetti M, Damonte G, Benatti U, Ferrara GB - J. Exp. Med. (2002)

Bottom Line: Macrophages exposed to macrophage colony-stimulating factor acquire the capacity to suppress T cell proliferation; this effect is associated with de novo expression of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO).Inhibition of cell proliferation induced by the tryptophan catabolites resulting from IDO activity was selective, applying only to cells undergoing activation.We suggest that IDO exerts its effect on cell proliferation by (i) starting the cascade of biochemical reactions that produce the three catabolites and by (ii) enhancing their inhibitory potential by depriving the extracellular microenvironment of tryptophan.

View Article: PubMed Central - PubMed

Affiliation: Immunogenetics Laboratory, National Cancer Research Institute, University of Genoa, Largo Rosanna Benzi 10, 16132 Genoa, Italy. guido.frumento@istge.it

ABSTRACT
Macrophages exposed to macrophage colony-stimulating factor acquire the capacity to suppress T cell proliferation; this effect is associated with de novo expression of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO). We have purified IDO and tested its activity in in vitro models of T cell activation. IDO was able to inhibit proliferation of CD4(+) T lymphocytes, CD8(+) T lymphocytes, and natural killer (NK) cells; proliferation of B lymphocytes was not affected. The inhibitory role of tryptophan and of its catabolites was then tested. In the presence of tryptophan, only L-kynurenine and picolinic acid inhibit cell proliferation. In a tryptophan-free medium cell proliferation was not affected. In the absence of tryptophan inhibition induced by L-kynurenine and picolinic acid was observed at concentrations below the lowest concentration that was effective in the presence of tryptophan, and quinolinic acid acquired some inhibitory capacity. Inhibition of cell proliferation induced by the tryptophan catabolites resulting from IDO activity was selective, applying only to cells undergoing activation. Resting cells were not affected and could subsequently activate normally. We suggest that IDO exerts its effect on cell proliferation by (i) starting the cascade of biochemical reactions that produce the three catabolites and by (ii) enhancing their inhibitory potential by depriving the extracellular microenvironment of tryptophan.

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Dose–response relationship to IDO for T cell proliferation. Increasing doses of IDO, together with 0.1 μM methylene blue and 200 μM l-ascorbic acid, were added at the beginning of the test to PHA-activated PBLs. Untreated cells were used as control. Cell culture was stopped at 96 h and proliferation was evaluated by measuring 3[H]thymidine incorporation (A) or by counting the cells in the cell cycle, as indicated in the Materials and Methods section (B). m ± 1 SD, n = 3.
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fig1: Dose–response relationship to IDO for T cell proliferation. Increasing doses of IDO, together with 0.1 μM methylene blue and 200 μM l-ascorbic acid, were added at the beginning of the test to PHA-activated PBLs. Untreated cells were used as control. Cell culture was stopped at 96 h and proliferation was evaluated by measuring 3[H]thymidine incorporation (A) or by counting the cells in the cell cycle, as indicated in the Materials and Methods section (B). m ± 1 SD, n = 3.

Mentions: The capacity of the purified enzyme to inhibit PBL proliferation was tested by adding the enzyme at increasing concentrations at the beginning of the test, together with methylene blue and l-ascorbic acid. These cofactors were added to optimize the efficiency of the enzyme, possibly by increasing production of O2− (13). Under these conditions a dose-dependent inhibition of cell proliferation was detected, both by evaluating 3[H]thymidine incorporation (Fig. 1 A) and by counting the cells entering the cell cycle (Fig. 1 B).


Tryptophan-derived catabolites are responsible for inhibition of T and natural killer cell proliferation induced by indoleamine 2,3-dioxygenase.

Frumento G, Rotondo R, Tonetti M, Damonte G, Benatti U, Ferrara GB - J. Exp. Med. (2002)

Dose–response relationship to IDO for T cell proliferation. Increasing doses of IDO, together with 0.1 μM methylene blue and 200 μM l-ascorbic acid, were added at the beginning of the test to PHA-activated PBLs. Untreated cells were used as control. Cell culture was stopped at 96 h and proliferation was evaluated by measuring 3[H]thymidine incorporation (A) or by counting the cells in the cell cycle, as indicated in the Materials and Methods section (B). m ± 1 SD, n = 3.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2196046&req=5

fig1: Dose–response relationship to IDO for T cell proliferation. Increasing doses of IDO, together with 0.1 μM methylene blue and 200 μM l-ascorbic acid, were added at the beginning of the test to PHA-activated PBLs. Untreated cells were used as control. Cell culture was stopped at 96 h and proliferation was evaluated by measuring 3[H]thymidine incorporation (A) or by counting the cells in the cell cycle, as indicated in the Materials and Methods section (B). m ± 1 SD, n = 3.
Mentions: The capacity of the purified enzyme to inhibit PBL proliferation was tested by adding the enzyme at increasing concentrations at the beginning of the test, together with methylene blue and l-ascorbic acid. These cofactors were added to optimize the efficiency of the enzyme, possibly by increasing production of O2− (13). Under these conditions a dose-dependent inhibition of cell proliferation was detected, both by evaluating 3[H]thymidine incorporation (Fig. 1 A) and by counting the cells entering the cell cycle (Fig. 1 B).

Bottom Line: Macrophages exposed to macrophage colony-stimulating factor acquire the capacity to suppress T cell proliferation; this effect is associated with de novo expression of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO).Inhibition of cell proliferation induced by the tryptophan catabolites resulting from IDO activity was selective, applying only to cells undergoing activation.We suggest that IDO exerts its effect on cell proliferation by (i) starting the cascade of biochemical reactions that produce the three catabolites and by (ii) enhancing their inhibitory potential by depriving the extracellular microenvironment of tryptophan.

View Article: PubMed Central - PubMed

Affiliation: Immunogenetics Laboratory, National Cancer Research Institute, University of Genoa, Largo Rosanna Benzi 10, 16132 Genoa, Italy. guido.frumento@istge.it

ABSTRACT
Macrophages exposed to macrophage colony-stimulating factor acquire the capacity to suppress T cell proliferation; this effect is associated with de novo expression of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO). We have purified IDO and tested its activity in in vitro models of T cell activation. IDO was able to inhibit proliferation of CD4(+) T lymphocytes, CD8(+) T lymphocytes, and natural killer (NK) cells; proliferation of B lymphocytes was not affected. The inhibitory role of tryptophan and of its catabolites was then tested. In the presence of tryptophan, only L-kynurenine and picolinic acid inhibit cell proliferation. In a tryptophan-free medium cell proliferation was not affected. In the absence of tryptophan inhibition induced by L-kynurenine and picolinic acid was observed at concentrations below the lowest concentration that was effective in the presence of tryptophan, and quinolinic acid acquired some inhibitory capacity. Inhibition of cell proliferation induced by the tryptophan catabolites resulting from IDO activity was selective, applying only to cells undergoing activation. Resting cells were not affected and could subsequently activate normally. We suggest that IDO exerts its effect on cell proliferation by (i) starting the cascade of biochemical reactions that produce the three catabolites and by (ii) enhancing their inhibitory potential by depriving the extracellular microenvironment of tryptophan.

Show MeSH
Related in: MedlinePlus